Pension And Other Postretirement Benefit Plans (Components Of Company's Net Periodic Benefit Cost) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1,603	$ 1,529	$ 4,691	$ 4,595
Interest cost	2,403	2,678	7,316	8,125
Expected return on plan assets	(3,676)	(4,151)	(11,032)	(12,557)
Net amortization and deferral	1,120	696	3,361	2,092
Net periodic benefit cost	1,450	752	4,336	2,255
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	48	53	145	159
Interest cost	286	322	859	986
Expected return on plan assets	(24)	(24)	(72)	(80)
Net amortization and deferral	(139)	(154)	(424)	(459)
Net periodic benefit cost	$ 171	$ 197	$ 508	$ 606